Binary star system

1. The problem statement, all variables and given/known data
2 stars rotating around the common centre of mass have masses m and 3m. What is the ratio of the force due to each star at the common centre of mass.

2. Relevant equations
None

3. The attempt at a solution
I tried to find the centre of mass and applied newtons law of gravitation F=(GMm)/R^2 to each star and solve i got the ratio 1:9. Is this correct?Thanks

It doesn't look right to me, but it is hard to tell without seeing the work.
How did you calculate the center of mass and how close to it are each of the masses? Did you remember that the force depends on the mass as well as the distance? Kind of odd that it asks for the force "at the center of mass" - there won't be a force unless there is a mass located there.